The impact of megafaunal loss and climate change on ecosystem functions in aridland ephemeral river systems

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Ephemeral river systems refer to rivers that only visibly contain water for a few weeks in a year, at most.This is usually because they are situated in hot, dry climates with very little rainfall. As such they areinvaluable to communities of humans and wildlife alike, because of the relative scarcity of water availableto them from other sources. Namibia has 12 of these ephemeral rivers running through the country, whichsupport rich and unique vegetation, provide agricultural services, and act as an oasis for migrating andendemic megafauna populations (Jacobson et al , 1995).Unfortunately, charismatic megafauna (terrestrial vertebrates heavier than 1000kg, Owen-Smith, 1988) isan uncommon sight in most of the Namibian rivers now, largely due to hunting and other human-wildlifeconflicts. This is bad news from a conservation perspective, but also from an economic perspective, aswildlife tourism contributes a significant amount towards Namibia's revenue (Jacobson et al , 1995). Itdoes provide a unique opportunity for experimentation, however. With similar river systems havingmegafauna persist in some but not others, we can compare the disparity of ecological processes betweenthe rivers, with relatively clear cause and effect.My PhD involves investigating the differences between these river systems using remote sensing data. Itshould also yield new data on the ecological roles of certain large animals using these systems,particularly elephants and giraffes.Modelling of climate effects are also a key component of this study for 2 reasons. The first pertains to theprevalence of ephemeral river systems in drylands, as expected changes to rainfall frequency and intensity,resulting from climate change, may drive other temporary rivers to become classed as 'ephemeral'(Larned et al, 2010; Tooth and Nanson, 2011). The second pertains to the relationship between climateand ecosystem. How the projected rainfall changes influence ephemeral river hydrology may be somewhatunderstood, but how said changes influence ecological processes within aquifer dependent ecosystems arenot (Eamus et al, 2006; Colvin et al, 2007). Thus, investigating rainfall change in these systems is integralto this project.